Polymer plastic film stretching device

The utility model relates to the technical field of plastic film processing, in particular to a polymer plastic film stretching device which comprises a bottom plate, a plurality of supporting plates, a plurality of transmission assemblies, two wind-up rollers, four mounting assemblies and three stretching rollers, each mounting assembly comprises a mounting piece and a fixing piece, each mounting piece comprises a pull ring, a fixing rod and two sliding plates, mounting columns are fixedly connected to the opposite sides of the two sliding plates, sliding blocks are slidably connected to the opposite sides of the two sliding plates, a connecting rod is rotatably connected between the opposite sides of the two sliding blocks, a fixing rod is driven by a pull ring, and the fixing rod drives one sliding plate connected with the fixing rod to extrude a spring and enables the connecting rod to rotate; the two ends of the connecting rod extend out gradually and drive the sliding blocks connected with the connectin